The detection of relative motion between mechanical members is used in many instruments. Measurement of physical forces within a system wherein electro-optical signals are generated, relative to position changes are in wide use. For example, diaphragms, bellows and bourdon tubes may be connected so that relative motion is developed when there are changes in the ambient pressure. Forces may be generated by weight, acceleration, temperature or other characteristics of the system.
The transduction of displaced motion into useful electrical data is widely used in many instrument applications. Previous systems have detected relative movement by the use of splitters, baffles and vanes between the light source and photosensitive detectors.
The present invention virtually eliminates previous system inaccuracies and lack of microsensitivity permits and easy adjustment. In the past, these systems have used only one photosensitive detector and no optical feedback. Therefore, these systems were subjected to electrical changes as a function of temperature, fatigue and optical drift. The symmetrical design of the pressure sensing elements and dual photosensitive detector, with optical feedback, eliminates the adverse effects of the prior art. Short and long term stability is achieved by a third photosensitive detector with electro-optical feedback from a light source into an electrically balanced circuit.
In order to obviate the aforementioned disadvantages of the prior art, the principle objects of this invention are to minimize inaccuracies, temperature and optical drift and to increase sensitivity and stability without internal adjustment, by use of symmetrical strut tube force sensing members and optical feedback for electro-optical stability.